Light control film (LCF), also known as light collimating film, is an optical film that is configured to regulate the transmission of light, often to obscure what is being viewed from others (for example, privacy film). LCFs are known and typically include a light transmissive film having a plurality of parallel grooves where the grooves are formed of a light-absorbing material. Various LCFs are described in, for example, U.S. Pat. No. 8,213,082 (Gaides et al.), U.S. Pub. No. 2008/0186558 (Lee et al.), U.S. Pat. No. 6,398,370 (Chiu et al.), etc.
LCFs can be placed proximate a display surface, an image surface, or other surfaces to be viewed. At normal incidence, (i.e. 0 degree viewing angle) where a viewer is looking at an image through the LCF in a direction that is perpendicular to the film surface, the image is viewable. As the viewing angle increases, the amount of light transmitted through the LCF decreases until a viewing cutoff angle is reached where substantially all the light is blocked by the light-absorbing material and the image is no longer viewable. This can provide privacy to a viewer by blocking observation by others that are outside a typical range of viewing angles.
LCFs can be prepared by molding and ultraviolet curing a polymerizable resin on a polycarbonate substrate. Such LCFs are commercially available under the trade designation “3M Filters for Notebook Computers and LCD Monitors” from Minnesota Mining and Manufacturing Company (“3M”) of St. Paul, Minn.
Conventional parallel grooved films are one-dimensional light control or privacy films, i.e. they have a light control effect only to the right and left (or up and down) of the film. A single sheet of conventional film thus cannot meet the user's need to ensure security in all directions including right-and-left and up-and-down of the film. In order to achieve a light control effect in various directions by a conventional light control film, two films could be overlapped with their louver directions crossing each other. However, this inevitably results in the problem of increasing the film thickness and decreasing the light transmittance.